UPDATE: 7PM EDT MONSTER TORNADO on LIVE WEBSTREAMING near Norman OK
Update by Ryan Maue
A Particularly Dangerous Situation (PDS) tornado watch (#356) has just been issued for Central Oklahoma and North Central Texas including DFW and OKC.
DESTRUCTIVE TORNADOES...LARGE HAIL TO 3 INCHES IN DIAMETER... THUNDERSTORM WIND GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.
Tornado likelihood is very high… SPC Convective Outlook:
...CENTRAL/SOUTHERN PLAINS... MORNING SATELLITE LOOPS SHOW A VIGOROUS AND PROGRESSIVE MID/UPPER LEVEL SHORTWAVE TROUGH OVER THE SOUTHERN ROCKIES. THIS FEATURE IS FORECAST TO ROTATE RAPIDLY EASTWARD INTO THE PLAINS AND BECOME NEGATIVELY-TILTED THIS EVENING. LATEST TCC PROFILER DATA SHOWS 90+ KNOT FLOW AT 6KM...INDICATIVE OF THE MID/UPPER LEVEL WIND MAX THAT WILL NOSE INTO THE PLAINS THIS EVENING. MEANWHILE... SOUTHERLY LOW LEVEL WINDS WILL MAINTAIN UPPER 60S AND LOWER 70S DEWPOINTS ACROSS MUCH OF NORTH TX...OK...AND SOUTHERN/CENTRAL KS. BY MID AFTERNOON THE DRYLINE WILL EXTEND FROM WEST-CENTRAL KS INTO WESTERN OK AND WESTERN NORTH TX. STRONG HEATING AND RICH MOISTURE...COUPLED WITH NEAR DRY-ADIABATIC MID LEVEL LAPSE RATES...WILL YIELD AN EXTREMELY UNSTABLE AIR MASS WITH MLCAPE VALUES OF 4000-4500 J/KG. PRESENT INDICATIONS AND LATEST OPERATIONS/MESOSCALE MODEL GUIDANCE INDICATE THAT DISCRETE SUPERCELL THUNDERSTORMS WILL FORM ALONG THE KS/OK DRYLINE BY MID AFTERNOON AND MOVE RAPIDLY NORTHEASTWARD WITH A RISK OF A FEW TORNADOES AND VERY LARGE HAIL. EARLY IN THE EVENT...THE GREATEST TORNADO THREAT WILL BE OVER KS AS STORMS INTERACT WITH PRE-EXISTING OUTFLOW BOUNDARY AND BACKED LOW LEVEL WINDS. AS THE AFTERNOON PROGRESSES...CONTINUED HEATING AND LARGE SCALE LIFT DUE TO APPROACHING UPPER TROUGH MAY LEAD TO MULTIPLE ROUNDS OF CONVECTIVE DEVELOPMENT ALONG THE DRYLINE. THESE STORMS WILL ALSO TRACK ACROSS THE HIGH RISK AREA DURING THE EVENING. LOW LEVEL WINDS WILL BE STRENGTHENING...WITH ALL CONDITIONS FAVORING THE POTENTIAL FOR LONG-TRACKED STRONG/VIOLENT TORNADOES AND VERY LARGE HAIL OVER PORTIONS OF NORTH TX...CENTRAL OK...AND CENTRAL KS
Real-time Forecast Links:
Tornado Probability -- Outlook issued 1625z May 24, 2011 NCEP 4-km Radar Forecast from two versions of the WRF model (ARW and NMM cores): 48-hour animation initialized at 12:00z on May 24, 2011 (from Ryan Maue’s FSU website)
============================================================== UPDATE: I’ve added my own radar product for people to watch, click the image to animate it:
If you want to track storms at the local level, download a free copy of StormPredator
John, we escaped any damaging hail, wind and ‘nadoes here as well … but that’s not to say there wasn’t weather just 5 miles away! Listening to the Collin County ARES net on 147.18 MHz there was ‘weather’ experienced by others, notably wind and hail and observed wall clouds. In Dallas and Tarrant counties proper experienced the fuller effects of hail and wind, and perhaps ‘nado action as well.
Now, a segue into a summary of reports from yesterday:
Map, 5-24-2011 Storm reports – http://oi53.tinypic.com/o6a9hz.jpg
Map and location/report data – http://www.spc.noaa.gov/climo/reports/110524_rpts.html
Thankfully, many of us escaped ‘the weather’; we should use the opportunity granted to assist those who were affected, because, surely, our ‘turn in the barrel’ will come about.
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It is done so, using automated techniques, since, doing it manually could easily employ half a dozen individuals (analyzing the multiple ‘level plots’ generated by a WSR-88D RADAR, observing for differential velocities, taking into account storm movement, etc) and this would become tedious; this was once the case (doing it manually) using the old WSR-57 and WSR-74 ‘network’ (although not using Doppler; an operator (or several RADAR ops) was actually stationed at a console which had direct control over the WSR-57 RADAR dish and electronics and his job was to analyze, summarize and make observations of RADAR returns as they appeared – there was no storage available aside from the persistence of the phosphor used in the PPI CRT).
Early WSR-88D Tornado Detection Algorithm (TDA):
http://www.nssl.noaa.gov/divisions/warning/swat/tda.php
This powerpoint (PPT) presentation explains how the WSR-88D (newer software) “Build 10 Tornado Detection Algorithm” works:
wx.db.erau.edu/faculty/mullerb/Wx365/Radar_nws/radarpt3.ppt
ADVANCED TORNADO DETECTION ALGORITHM USING SUPER-RESOLUTION
AND POLARIMETRIC DATA
ams.confex.com/ams/pdfpapers/155969.pdf
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They still use human observation ground truth from Skywarn spotters to confirm what the radar is telling them. On many occasions when chasing storms NWS would call us and ask us what we were seeing, then moments after our report the severe warning would go out.
They need the ground truth to sort out some issues that the radar simply cannot tell them. Hail and heavy rain can sometimes be confused, and it really helps to get spotter confirmation that there is in fact a hail signature rather than heavy precipitation.
In addition, the radar cannot see all the way to the ground at a significant distance from the radar due to the curvature of the earth. They may be seeing mid level circulation at the lowest tilt sweep when the storm in 50-100 miles from the radar, and human observation confirming the existence of wall clouds and low level circulation is important to minimize over warning.
One of the problems is the general public has little appreciation of how local storm conditions can be. As a spotter I have dodged 2.5 inch hail on one side of a storm and just a couple miles away another spotter was sitting in bright sunshine and light winds. I have also been less than 1/2 mile from a large tornado and unable to even see it. I have had to drive around for a considerable time to find destructive hail swaths that are only a couple hundred yards wide and a 1/2 mile long. In open country, unless you know what to look for, you can drive right through a tornado path a few hours after it happened and never have a clue it had happened.
During the Last Chance tornado here in Colorado years ago, it put down several small funnels then formed a 1/4 mile wide wedge on the ground that tracked for several miles through farm country. It did remarkably light damage for the size of the storm simply because it failed to hit much. It slam dunked a few cattle killing them, tore up a farmers wind mill and made a grazing hit on the Chris Davis farm, pulled the roof off a barn (leaving a lantern hanging on a post peg untouched) tossing 25′ diameter grain bins a 1/4 of a mile, blowing all the windows out of 3 combines in the field, tried to pickup a household propane tank and spun it around a few times breaking the gas connections, leveled an old steel arch (Quonset hut style) garage, and carried a steel tank 12′ in diameter, and 20 ft long a 1/2 mile, and almost pulled the house off its foundation.
In spite of that long track and its size, it only took down about 3 power poles according to the rural electric crews I talked to that day. If you had not known a tornado had tracked through the area the day before, and did not come within site of the Chris Davis farm you never would have known it had happened except for a couple dead cattle in the fields.
When the wedge first formed, I was less than a mile away on the southwest side and only could see it for a few seconds before it rain wrapped and got swallowed up in the mist and rain.
Larry
Here’s what’s on tap:
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ON SUNDAY AN UPPER LOW IS FORECAST TO MOVE SOUTHWARD OVER NORTHERN CALIFORNIA BEFORE HEADING EAST TOWARDS THE GREAT BASIN. THERE ARE DIFFERENCES IN MODEL SOLUTIONS REGARDING THE WESTWARD EXTENT OF THIS LOW`S PATH…THUS WHETHER OR NOT THERE WILL BE ANY SHOWER CHANCES FOR OUR CWA. THE EARLIER RUN OF THE GFS TOOK THIS LOW FARTHER TO THE EAST FOR A COOL BUT DRY SOLUTION FOR OUR AREA… WHEREAS THE ECMWF HAS THE LOW CENTER ITSELF OVER SAN FRANCISCO BY SUNDAY MORNING. THIS WOULD WARRANT PUTTING SOME SHOWER CHANCES INTO OUR FORECAST FOR THAT DAY.
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This one will hit the S. Plains early / mid next week, unless a good blocker builds north from the Gulf.
Sorry, forgot to mention that today’s front (e.g. the one I described bearing down on us yesterday) is also a good cold pool. Raining here right now (almost unheard of this late in the season).
We had a big circulation pass over my house last night. It did some damage to the west (probably a tornado) but by the time it reached my area the circulation was becomming disorganized. Still, once the rain and hail had passed and I knew it was safe, I used this as an excellent opportunity to teach my kids about weather. We counted four small circulating cloud bulges before it had moved on.
The Hinton – Langston tornado track in Oklahoma happily died down to F1 near Stillwater as it crossed north of our mobile home – the little wind turbine vent on top the storm cellar set up quite the buzz as the tornado passed by.
See the other thread. Yesterday’s cold pool produced tornadic events here in California.